Daily Groundwater Monitoring Using Vehicle-DAS Elastic Full-waveform Inversion

Understanding groundwater dynamics is critical for sustainable water management, particularly as climate extremes intensify. However, the resolutions of existing subsurface observational tools are still inadequate for detailed aquifer monitoring and imaging. We introduce an innovative technique for groundwater monitoring using time-lapse full-waveform inversion, leveraging fiber-optic cables as seismic sensors and vehicular traffic as repetitive seismic sources. Over a two-year period along Sandhill Road, California, this approach captures detailed spatiotemporal S-wave velocity variations, revealing a 2.9% reduction corresponding to a 9.0-meter groundwater table rise after atmospheric-river storms in Water Year 2023. Notably, this approach enables the high-resolution daily analysis of rapid aquifer responses. We observe spatially inhomogeneous velocity changes, with less reduction beneath impervious paved zones than under grassy areas, underscoring the impact of urbanization on the natural recharge of aquifers. Our findings highlight the potential of Vehicle-DAS FWI for high-resolution daily monitoring and quantitative spatiotemporal characterizations of groundwater systems.